The present invention relates to the combination of a vertical axis Savonius-type rotor, a deflector plate device which serves as an augmentation apparatus that considerably increases the power output of the Savonius-type rotor and also improves its self-starting ability and smoothness of operation, and a fantail member to correctly orientate the deflector plate device. In connection with the above combination, the invention also features a simple, automatic speed control mechanism which can be used to control the speed of the rotor in high winds.
As used in this application, the term "Savonius rotor" includes rotors having a shape as generally illustrated in this application and in U.S. Pat. No. 4,359,311, as well as rotors with two or more blades of the classic Savonius type, wherein the rotor blades are generally semi-cylindrical in shape. This is in contrast to turbines which have the inner edges of the blades fixed to adjoining blades or to a central core, drum or shaft in such a manner that there can be practically no crossing of the fluid past the inner edges of the blades.
High speed propellor-type turbines have dominated the wind energy field largely because of their relatively high efficiency. Slow speed turbines such as the Savonius vertical axis turbine or the multi-blade horizontal axis windmill used for pumping water have typically been of low efficiency and cannot compete with the high speed propellor type for electrical power production. In addition to other disadvantages, however, there are some places where the high speed propellor-type turbine cannot be installed. For example, such a turbine cannot be placed on top of large area flat buildings because the wind would be too unstable, and also the turbines would be too dangerous. With the high speed turbine, safety is an important consideration, and since metal fatigue is related to the number of stress reverses of high magnitude, it is difficult to predict when a blade may come loose from the turbine.
As indicated in applicant's U.S. Pat. No. 4,359,311, Savonius-type rotors have well-known problems associated therewith. For example, they have low starting torque when oriented at certain directions and their action is jerky and pulsating under a load.
The present invention provides the combination of a two-blade Savonius-type rotor of considerably improved efficiency, and considerably better self-starting characteristics than the classic semicylindrical-blade two-blade rotor, a deflector plate which gives operating improvement to the rotor, in addition to considerably increasing the power output, and a fantail member for keeping the deflector plate in the most advantageous position. In addition, the present invention provides a speed regulator mechanism for protecting the rotor in high winds, while producing power at the same time. The two-blade Savonius-type rotor used in the present invention is set out in applicant's U.S. Pat. No. 4,715,776.
The present invention solves the above problems as well as other problems associated with existing designs.